Passive filter design for reducing harmonics in light emitting diode bulb

Transcription

1 Passive filter design for reduing harmonis in light emitting diode bulb Rambe Ali Hanafiah 1*, Muhammad Safril 1, and Suherman Suherman 1 1 Universitas Sumatera Utara, Eletrial Engineering Department, Medan, Indonesia Abstrat. Harmonis redue power quality and inrease ineffiieny. Although light emitting diode (LED) bulb has been onsidered more effiient than previous bulb tehnologies; its internal iruits potentially generate additional problems. This paper has surveyed 6 LED bulb samples and measured the harmonis generated by the internal iruits. As a result. 7 Watt type B LED bulb produes the highest 3rd order harmonis urrent whih is inompatible with IEC Class C. A prototype of LC filter is designed to derease the harmoni level. The measurement shows that the designed passive filter is able to redue at least 81.3% of harmonis. 1 Introdution Light emitting diodes (LED) is designed to fulfil the neessity of effiient light bulb as lighting onsumes about 20% of total world energy [1][2]. LED bulb is supplied by eletriity soure through an AC/DC onverter, driving light ontroller iruits [3]. This flybak iruit as shown in Figure 1, has transformer and apaitor that potentially produe harmonis. The primary oil is to ontrol voltage on fly-bak. This bootstrap oil ontrols the transistor and MOSFET voltages. When starting up. No power produed in bootstrap. Therefore; the start-up regulator suh as LR645 and LR8 are employed. After bootstrap produes power, the regulator is off. This fly-bak iruit is built in the LED bulb as in Figure 2. Swithing on MOSFET fly-bak iruit results eletri waveforms whih are different from the fundamental one [4]. It results harmoni distortion. Harmoni is defined as a urrent or a voltage that has frequeny folding of its fundamental [5]. These harmonis are unwanted in eletrial system. Third harmoni distortion (THDi and THDv) are used to measure harmoni level [6]. In order to omply with IEC Class C requirement, these harmonis should be redued. This paper reports harmoni redution on LED bulb through simulation and implementation. Farad 50 V 680 Ohm SF18 kilo Ohm Farad Ohm n Farad Farad Fig. 1. Fly-bak iruit. Fig. 2. LED bulb. 2N60 MOSFET B BZT52C6V2 6,8 Farad p Farad 100 V n Farad C kilo Ohm E Fuse Sumber AC 2 Researh methods Table 1 plots survey results on harmonis generated by the 6 seleted LED bulb of 7 Watt. The survey employed power Q fluke 435 and the power logi PM5330 Shneider eletri. The harmoni is bigger than the permitted threshold; as standardized by IEC lass C. * Corresponding author: ali3@usu.a.id The Authors, published by EDP Sienes. This is an open aess artile distributed under the terms of the Creative Commons Attribution Liense 4.0 (

2 Parameters Phase Voltage (V) Phase Current(A) Table 1. Harmonis in LED bulbs. LED Bulb 7 watt A B C D E F basi of LC filter design. Figure 4 represents the system in simulation. Power(VA) Ative Power (W) Reative Power(VAR) Frequeny (Hz) Power Fator THDv THDi As shown in Table 1, LED B has the highest THDi %. The third order harmoni is 90.3%, the fifth is 76.1%. The 7th, 9th, 11th, 13th and 15th are 58.6%, 42.1%, 31%, 27% and 26%. Based on this fat, the designed filter is intended for overoming harmonis in LED bulb B. This researh performs simulation and implementation of passive filter design. Simulation is to mimi the real situation. Afterward, L and C values are alulated. In implementation, indutor is designed by using transformer, reating multiple indutor networks. The result is then tested by using either simulation or measurement. Figure 3 shows the snapshots of harmoni values generated by LED bulb B whih is used as the Fig. 3. Snapshots of LED B Harmonis. Fig. 4. Simulation model. 2

3 By using data on Figure 3, the load urrent is alulated by using: Based on harmonis orde: = 0.05 A (1) The power onsumed for power fator 0.51is: P = x 0.05 x 0.51 = watt (2) If it is assumed that power fator is orreted to 0.98, the load urrent is: = 0.026A (3) Then: The indutor (L) is: (12) (13) (14) The apaitor is alulated by using: Q C = P(tan φ awal tan φ target ) (4) Q C = 5.5(tan tan ) (5) Q C = 5.5 ( ) (6) Q C = 5.5 (1.49) = 8.16 VAR (7) The apaitor value for 8.16 VAR is: This value is then examined by applying this LC to system model in Figure 4 and implemented by using real iruit. 3 Simulation results By loating the alulated LC parallel to the system model on Figure 4, the harmoni redution an be analysed. The filter position is illustrated in Figure 5 and simulation model is depited in Figure 6. The indutor is alulated as: and: (8) F= F (9) (10) Farad 50 V 680 Ohm SF18 kilo Ohm Farad Ohm n Farad Farad 2N60 MOSFET B BZT52C6V2 6,8 Farad p Farad 100 V n Farad C kilo Ohm E Fuse 0,562 miro Farad Filter Pasif LC 13,6 Hendry POWER Analyzer Clamp CT Tegangan Sumber AC (11) Fig. 5. Filter position. Fig. 6. Filter insertion on model. * Corresponding author: ali3@usu.a.id 3

4 Simulation shows that the inserted LC filter is able to redue harmonis values as outline in Table 2. Table 2. Simulation results. Parameter Before After Phase Voltage (V) Phase Current(A) Power Fator THDv THDi Frequeny (Hz) Orde Orde Orde Orde Orde Orde Orde Orde Implementation results Capaitor is easily found in market. However, indutor is triky to design. In order to produe H indutor, the size and number of turn are alulated as follows: The harmonis value after measuring the implemented filter is shown in Table 3. Table 2. Simulation results. Parameter Before After Phase Voltage (V) Phase Current(A) Power Fator THDv THDi Frequeny (Hz) Orde Orde Orde Orde Orde Orde Orde Orde The omparison harmonis in LED bulb, simulation with LC filter and measurement with LC filter is shown in Figure 8. = 0,95 (15) h = The surfae area is: = 1,43 m (16) A = b x h = 0,95 x 1,43 m 2 (17) The designed indutor onsist of 8 indutor of 1.7 H made of transformer. For eah indutor, number of turn is: (18) = 526 turns Turn diameter is: = 0,1 mm (19) The air gap is: x 10 4 = 2,75247 x10-5 (20) Its realization is shown in Figure 7. Fig. 7. Filter implementation. Fig. 8. Performane omparison. Based on Figure 8, by adding LC filter with C=0.562 μf and L=13.64 H is simulation model, the total urrent harmonis (THDi) is redued 91% and average individual harmoni urrent dereases to 96.3%. By implementing the LC filter uses apaitor and transformer; THDi dereases THDi up to 89.80% and average individual harmoni urrent (IHDi) 91 %. 5 Conlusions It has been shown that even LED bulb is design to effiiently using the eletriity; its internal iruit produes harmonis. By proposing a simple LC filter, the THDi and IHDi are suessfully redued. The simulation show that LC filter produes 91% THDi and average individual harmoni urrent dereases to 96.3% while real implementation gives THDi 89.80% and IHDi 91 %. * Corresponding author: ali3@usu.a.id 4

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